For our initial sample, children with Attention-Deficit/Hyperactivity Disorder (ADHD) participated in double-blind placebo-controlled randomized trails of stimulants while undergoing anatomic imaging with magnetic resonance imaging (MRI). The children are now being followed, with repeated clinical and neuroanantomic assessments every 2 years. Genetic studies are being conducted in tandem, allowing links to be made between genes, clinical outcome and brain development. Key findings include (1) ADHD children with good outcome have a different regional brain trajectory in the posterior parietal region and cerbellar hemispheres suggesting compensatory plasticity, (2) the most commonly implicated risk gene for ADHD (the 7-repeat form of the gene for the dopamine D4 receptor) is related to cortical thinning in childhood and good outcome during adolescence. Unpublished data suggests that cortical development in ADHD children as a group is delayed by several years. This suggests that a good outcome subgroup is merely developmentally delayed while others may have a different brain developmental pattern. A large sample is being gathered in order to follow more remitted and non-remitted adolescents to test this hypothesis. A sample of adult subjects is also being collected to test the hypothesis that good outcome adults are able to use the parietal region to supplement frontal lobe hypofunction.